Rabaptin-5 is a direct effector of the small GTPase Rab5 in endocytic membrane fusion
H Stenmark, G Vitale, O Ullrich, M Zerial - Cell, 1995 - cell.com
H Stenmark, G Vitale, O Ullrich, M Zerial
Cell, 1995•cell.comWe have identified a novel 100 kDa coiled-coil protein, rabaptin-5, that specifically interacts
with the GTP form of the small GTPase Flab& a potent regulator of endocytic transport. It is
mainly cytosolic, but a fraction colocalizes with Rab5 to early endosomes. Expression of a
GTPase-deficient Flab5 mutant enhances the binding of rabaptin-5 to enlarged endosomes.
Overexpression of rabaptin-5 alone is sufficient to promote expansion of early endosomes.
Rab5 recruits rabaptin-5 to purified early endosomes in a GTP-dependent manner …
with the GTP form of the small GTPase Flab& a potent regulator of endocytic transport. It is
mainly cytosolic, but a fraction colocalizes with Rab5 to early endosomes. Expression of a
GTPase-deficient Flab5 mutant enhances the binding of rabaptin-5 to enlarged endosomes.
Overexpression of rabaptin-5 alone is sufficient to promote expansion of early endosomes.
Rab5 recruits rabaptin-5 to purified early endosomes in a GTP-dependent manner …
Summary
We have identified a novel 100 kDa coiled-coil protein, rabaptin-5, that specifically interacts with the GTP form of the small GTPase Flab& a potent regulator of endocytic transport. It is mainly cytosolic, but a fraction colocalizes with Rab5 to early endosomes. Expression of a GTPase-deficient Flab5 mutant enhances the binding of rabaptin-5 to enlarged endosomes. Overexpression of rabaptin-5 alone is sufficient to promote expansion of early endosomes. Rab5 recruits rabaptin-5 to purified early endosomes in a GTP-dependent manner, demonstrating functional similarities with other members of the Ras superfamily. Immunodepletion of rabaptin-5 from cytosol strongly inhibits Rab5-dependent early endosome fusion. Rabaptin-5 is thus a Rab effector required for membrane docking and fusion.
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